It is a good question because both in the USA and the UK the thievery of pet cats and dogs is on the rise. In the UK, for example, thefts of cats has risen by forty percent in the past two years according to a survey. Less than twenty percent are recovered by the police. In the UK up to 360,000 cats are stolen per year with the Bengal being top of the list. I think that is more than are killed on the roads.
In the USA the American Kennel Club has been reported on stolen dogs since 2007 and has seen a thirty-one percent increase in recent years. One issue is that the owners sometimes believe that their cat is lost but not stolen. That’s their first thought. There will be little or no evidence of theft if the cat is an indoor/outdoor cat.
So, where are stolen cats sold? Well sometimes they are not sold but kept because the person is a one-off thief and they fancy owning the cat. For professional thieves, the common sense answer is that they advertise online or approach other people individually, person-to-person, to sell their stolen cats. It must be difficult to trace these adverts because there are so many outlets.
The owner may believe that their cat is lost whereas in fact he/she has been stolen. The thief waits a bit and then claims they have found the cat and demands a reward. This is theft and blackmail.
If the cat is neither spayed nor neutered then the thief might try and sell the cat to a cat breeder if the cat is of sufficient quality to be acceptable to a breeder. Failing that, the cat can be sold to an illicit or illegal backstreet breeder running a kitten mill. I suspect that some of these cats might be shipped out abroad to continental Europe from the UK, specifically to Eastern Europe where there are known puppy farms and kitten mills.
I would hope rarely, sometimes disgruntled neighbours steal someone else’s cat and dump them somewhere far away from where they live because they are fed up with the cat peeing or defecating on their back garden. This may be a scenario which sometimes rears its ugly head.
In the past, stolen cats were sold to class B dealers in the USA. These were dealers who sold the cats on to animal testing laboratories. This has been banned in the USA in 2016. Specifically funding of USDA Class B licenses for dealers selling “random source” dogs and cats to medical research was banned.
Finally, although dog fighting is illegal (a felony in all 50 states of the US) and in the UK, sometimes stolen cats might be handed onto the people who arrange dogfighting in order to train the dogs to kill and prepare them for a fight. That is my understanding of the situation.
Some more on stolen cats